How to replace text over multiple lines using preg_replace

Question

Hi have the following content within an html page that stretches multiple lines

<div class="c-fc c-bc" id="content">
                <span class="content-heading c-hc">Heading 1 </span><br />
                The Home Page must provide a introduction to the services provided.<br />
                <br />
                <span class="c-sc">Sub Heading</span><br />
                The Home Page must provide a introduction to the services provided.<br />
                <br />
                <span class="c-sc">Sub Heading</span><br /> 
                The Home Page must provide a introduction to the services provided.<br />
            </div>

I need to replace everthing between <div class="c-fc c-bc" id="content"> and </div> with custom text

I use the following code to accomplish this but it does not want to work if it's multiple lines, but works if evertinh is in one line

$body = file_get_contents('../../templates/'.$val['url']);

$body = preg_replace('/<div class=\"c\-fc c\-bc\" id=\"content\">(.*)<\/div>/','<div class="c-fc c-bc" id="content">abc</div>',$body);

Am I missing something?

For multiline/dotall regex you'll also want to be very careful with that greedy .*, which will cause the very last </div> end-tag on the entire page to be matched. Maybe you want the first </div> end-tag in which case you'd need a non-greedy .*?. If you want the matching </div> end-tag, there is no way regex can work that out. Did we mention, don't use regex to parse HTML? — bobince
– bobince, Commented Jan 20, 2010 at 14:22

Mark Byers · Accepted Answer · 2010-01-20 12:54:51Z

42

If this weren't HTML, I'd tell you to use the DOTALL modifier to change the meaning of . from 'match everything except new line' to 'match everything':

preg_replace('/(.*)<\/div>/s','abc',$body);

But this is HTML, so use an HTML parser instead.

answered Jan 20, 2010 at 12:54

Mark Byers

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1 Comment

nitigyan Over a year ago

works great!. I was trying by replacing new lines with trim(preg_replace('/\s\s+/', ' ', $input)) . It was working with PHP test run online but was not working in my code.

Will Earp · Accepted Answer · 2010-01-26 11:45:50Z

24

it is the "s" flag, it enables . to capture newlines

answered Jan 26, 2010 at 11:45

Will Earp

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1 Comment

Benjamin Over a year ago

Documentation for PHP: s (PCRE_DOTALL) If this modifier is set, a dot metacharacter in the pattern matches all characters, including newlines. Without it, newlines are excluded. This modifier is equivalent to Perl's /s modifier. A negative class such as [^a] always matches a newline character, independent of the setting of this modifier.

meistermuh · Accepted Answer · 2018-04-17 14:36:36Z

1

you can also use [\s\S] instead of . combined with the DOTALL flag s for matching everyting because [\s\S] means exactly the same: match everything; \s matches all space-characters (including newline) and \S machtes everything that is not a space-character (i.e. everything else). in some cases/implementations of regular expressions, this works better than enabling DOTALL

caution: .* with the flag for DOTALL as well as [\s\S] are both "hungry" and won't stop reading the string. if you want them to stop at a certain position, (e.g. the first </div>), use the non-greedy operator ? behind your quantifier, e.g. .*?

edited Apr 17, 2018 at 14:36

answered Apr 17, 2018 at 14:20

meistermuh

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Comments

Al. · Accepted Answer · 2012-02-06 23:17:43Z

0

It is possible to use regex to strip out chunks of html data, but you need to wrap the html with custom html tags which get ignored by browsers. For example:

<?php
$html='
<div>This will be shown</div>
<custom650 rel="nofollow">
  <p class="subformedit">
    <a href="#" class="mylink">Link</a>
    <div class="morestuff">
      ... more html in here ...
    </div>
  </p>
</custom650>
<div>This will also be shown</div>
';

To strip the tags with the rel="nofollow" attributes, you can use the following regex:

$newhtml = preg_replace('/<([^\s]+)[^>]*rel="nofollow"[^>]*>.*?<\/\1>/si', '', $html);

From experience, start the custom tags on a new line. Undoubtedly a hack, but might help someone.

answered Feb 6, 2012 at 23:17

Al.

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